The present invention relates to hole formation in a machine component and more specifically to a method for determining whether a hole is blocked or is completely formed through a turbo-machinery component wall.
Airfoils in a turbine engine often include cooling holes for discharging a film of cooling air along the outer surface of the airfoil to affect film cooling. These may be referred to as “film cooling holes” or “film holes.”
Generally, cooling holes extend through a wall in an aircraft component from an entry end to an exit end. It is critical that these holes be formed completely through the respective component. In order for proper cooling, all cooling holes should be formed completely through the wall of the component. Blocked holes will result in overheated areas or “hotspots.” Blocked holes can be the result of incomplete hole formation or of debris in the hole.
One problem with current methods for producing cooling holes is that it is very difficult and time-consuming to determine whether a cooling hole is properly formed through the wall of the component. If one or more holes are not formed properly, the component is reworked and the blocked holes are re-drilled. In order to re-drill a hole, the equipment must be repositioned over the hole.
Conventional methods of verifying whether a cooling hole is properly formed include pin checks and water checks. Pin checks require an operator to manually insert a pin into the hole to determine whether the pin passes completely through the associated wall. In water checks, water pressure is applied within an airfoil and the hole is observed to determine whether water passes through it. Both of these methods have associated problems. The pin check method is manual and can result in repetitive motion injuries. The water check method can be inaccurate. Therefore there is a need for a method for forming cooling holes through aircraft components which incorporates a step of verifying whether a cooling hole is properly formed through the component or is blocked and for reworking such a hole before another hole is started.